This invention relates to a computer system including an active system and a standby system, and more particularly, to a technology which provides data managed by the computer system.
In a conventional cluster system which duplicates process data using computers in an active system and a standby system as well as a shared disk of a nonvolatile recording medium, when a failure occurs in the active system, the standby system accesses the process data held on the nonvolatile recording medium to switch the systems and recover the failure, thereby allowing a process to be continued.
In recent years, a cluster system has appeared which uses, to improve an I/O processing speed and hold process data, a volatile memory as a volatile recording medium instead of using the shared disk of the nonvolatile recording medium. In such a cluster system, the process data held in the volatile memory cannot be shared between the active system and the standby system, and hence the process data is lost in the event of a failure in the active system. To prevent this, the active system transfers update information on the process data held in the volatile memory to the standby system, while the standby system copies the update information received thereby in the process data held in the volatile memory of its own to duplicate the process data, and ensures redundancy. In the case where high failure tolerance is required, a plurality of the standby systems are provided, and the active system simultaneously transfers the process data to the plurality of standby systems.
However, in the cluster system having the standby system as a system switching destination in the event of a failure, the standby system is not efficiently used for data processing while the active system normally operates. This leads to the problem of low resource usability.
As a solution to the problem, in addition to the application which uses the standby system as the switching destination in the event of a failure, it can be considered to cause the plurality of standby systems to process a reference request, and cause the active system to process an update request so as to improve the data processing performance of the entire system, and efficiently use the resources of the standby systems. JP 2002-63055 A discloses a technology which distributes, in a cluster system where data is stored on a volatile recording medium, an update request and a reference request to a plurality of computers so that the update request and the reference request are processed thereby.